Application of Nuclear Magnetic Resonance to the Study of Liver Physiology and Disease

Abstract

Technological advances in nuclear magnetic resonance (NMR) have occurred at a rapid pace in recent years. As a result of a series of significant innovations, NMR, which only a decade ago was considered to be largely a tool of the structural chemist, has assumed a place of growing importance as a noninvasive technique in biomedical research. As noted in previous reviews (1-4), it is now possible to make measurements on metabolites in intact cells, subcellular organelles, and isolated perfused organs and obtain the same sort of detailed information about structure, reaction rates, and binding sites that has been available from NMR studies of purified biomolecules in solution. Some phenomena, however, are observable only in the whole cell; these include intracellular pH, ApH across the plasma membrane, and ApH across the mitochondria1 membrane, which have all been measured in uiuo by phosphorus-31 ("P) NMR. The concentrations of phosphorylated metabolites, such as adenosine triphosphate (ATP) and inorganic phosphate (Pi), are measured simultaneously and repetitively; thus, their levels can be followed with time for correlation with changes in ApH or the onset of a period of ischemia or hypoxia. In the carbon-13 (13C) NMR experiments discussed here, in which 13C-enriched substrates are metabolized in isolated rat liver cells and perfused liver, signals from intermediates and endproducts are observed, and the distribution of the "C-label in these metabolites is used to elucidate pathways and kinetics. The NMR method has the advantage of simultaneously detecting all metabolites that have been adequately labeled. This property makes NMR especially useful in advancing our understanding of the complex responses of the cell to hormonal stimulation or to direct challenges from specific enzyme inhibitors. Since 13C and 31P nuclei frequently yield complementary data, the simultaneous observation of both 13C and 31P NMR spectra can supply a panoply of information on the regulation of metabolism in uiuo. In our latest study of hepatic metabolism (5) NMR studies of liver metabolism now include several 31P and 13C high-resolution NMR investigations of metabolism in respiring isolated rat liver cells (6-lo), isolated perfused mouse (9-12), and rat (5, 13) liver, and preliminary in uiuo 31P (14) and 13C (15) studies in rat liver.The most rapidly expanding medical application of NMR-clinical NMR imaging-will be mentioned only briefly because the instrumentation that NMR imaging methods require and the range of application of these methods differ greatly from those of the high-resolution NMR techniques which are the major focus of this review. Proton (lH)NMR imaging is currently being used to detect liver disease in humans (16-18) and in experimental animals (19,20). Before describing specific applications of NMR to liver physiology, it is useful to consider briefly the principles of the Fourier transform (FT) NMR technique, concentrating on the properties to be mentioned later; full, but quite readable, introductions to FT-NMR have ...

In-cell NMR: Why and how?

“…Initially, systems to perfuse organs were used in the 1970-80's, mostly to monitor ion equilibria or metabolism in rat or rabbit hearts [277,378,807,812,818,[856][857][858][859]861,[1786][1787][1788][1789], livers [725][726][727]809,814,[1790][1791][1792][1793][1794] and kidneys [808,819], using 31 P-, 23 Na- 13 C-or 1 H-detected NMR [1795][1796][1797]. Perfusion systems for NMR spectroscopy of living plants were also proposed [884][885][886]900,1798].…”

In vivo assessment of intracellular redox state in rat liver using hyperpolarized [1‐13C]Alanine

“…These chemical methods, however, require cell extraction and thus cannot be used for in vivo studies. The ratio of carbon‐13 ( 13 C)‐labeled lactate and pyruvate, as measured by magnetic resonance spectroscopy (MRS) after administration of 13 C‐labeled glucose, allows noninvasive in vivo assessment of redox state (reflecting the intrinsic pool sizes of endogenous lactate and pyruvate) but has low sensitivity, and the long measurement times increase sensitivity to potential metabolic perturbations from the 13 C‐labeled substrate.…”

Hepatic Imaging: Positron Emission Tomography, Digital Angiography, and Nuclear Magnetic Resonance Imaging

“…'H and '?lP are the naturally abundant isotopes; '3C is only 1% naturally abundant. Phosphorus and possibly hydrogen spectroscopy are likely to prove clinically useful; carbon spectroscopy is more likely to prove limited to laboratory and small animal use since isotopically enriched compounds usually need to be given; NMR spectroscopic applications were described in detail in a previous issue of Hepatology (1).…”

“…positron emission tomography, digital angiography, and nuclear magnetic resonance imaging (NMR)]. Theoretical and research applications of NMR technology were discussed in the September-October issue of Hepatology (1).…”

“…research applications of NMR technology were discussed in the September-October issue of Hepatology (1).…”